Performance and Design of Straight, Two-Dimensional Diffusers

1967 ◽  
Vol 89 (1) ◽  
pp. 141-150 ◽  
Author(s):  
L. R. Reneau ◽  
J. P. Johnston ◽  
S. J. Kline
Keyword(s):  
Boundary Layer ◽  
Flow Regime ◽  
Flow Characteristics ◽  
Performance Data ◽  
Center Line ◽  
Two Dimensional ◽  
Rational Basis ◽  
Primary Flow ◽  
Wide Range ◽  
And Performance

Performance data and flow characteristics for subsonic, two-dimensional, straight center line diffusers are presented. The four primary flow regimes which can occur are described and presented as functions of overall diffuser geometry. The performance of both stalled and unstalled diffusers is mapped for a wide range of geometries and inlet boundary layer thicknesses. An understanding of the relationships between flow regime and performance leads to a rational basis for diffuser design. The important maxima of performance and their location on the performance maps are presented. Both the range of data and correlations of optima of performance are extended beyond previous results.

The Design and Performance of Two-Dimensional, Curved Diffusers: Part I—Exposition of Method and Part II—Experiment, Evaluation of Method, and Conclusions

1967 ◽  
Vol 89 (4) ◽  
pp. 715-731 ◽  
Author(s):  
C. J. Sagi ◽  
J. P. Johnston
Keyword(s):  
Flow Regime ◽  
Outer Wall ◽  
Center Line ◽  
Two Dimensional ◽  
Pressure Distributions ◽  
Wall Potential ◽  
Straight Wall ◽  
Throat Width ◽  
Flow Pressure ◽  
And Performance

A procedure for the design of two-dimensional, curved diffusers is developed and evaluated through comparisons with flow regime and performance data. As input to the method, the inner and outer-wall potential-flow pressure distributions are specified as combinations of straight-wall diffuser pressure distributions. The diffuser shape is calculated using the method of Stanitz. In Part II criteria are established for choosing desirable inner and outer-wall pressure distributions. These criteria are based on systematic performance and flow regime tests carried out on curved diffusers with inner-wall length to throat width ratios between 4 and 10, area ratios between 1.5 and 2.1, and turning angles between 30 and 90 deg. The procedure yields diffusers of higher performance than circular-arc center-line diffusers.

Heat and Mass Transfer in an Incompressible Turbulent Boundary Layer

1972 ◽  
Vol 94 (1) ◽  
pp. 23-28 ◽  
Author(s):  
E. Brundrett ◽  
W. B. Nicoll ◽  
A. B. Strong
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Porous Plate ◽  
Mixing Length ◽  
Two Dimensional ◽  
Transfer Data ◽  
Incompressible Turbulent Boundary Layer ◽  
Wide Range ◽  
Incompressible Boundary

The van Driest damped mixing length has been extended to account for the effects of mass transfer through a porous plate into a turbulent, two-dimensional incompressible boundary layer. The present mixing length is continuous from the wall through to the inner-law region of the flow, and although empirical, has been shown to predict wall shear stress and heat transfer data for a wide range of blowing rates.

Experimental Investigations of Laminar, Transitional to Turbulent Gas Flow in a Micro-Channel

2010 ◽  
Author(s):  
Chungpyo Hong ◽  
Toru Yamada ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Koichi Suzuki ◽  
...  
Keyword(s):  
Mach Number ◽  
Flow Regime ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Channel Length ◽  
Transitional Flow ◽  
Experimental Investigations ◽  
Compressibility Effect ◽  
Micro Channels ◽  
Wide Range

This paper presents experimental results on flow characteristics of laminar, transitional to turbulent gas flows through micro-channels. The experiments were performed for three micro-channels. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter are 69.48, 99.36 and 147.76 μm. The pressure was measured at seven locations along the channel length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. Flow characteristics in transitional flow regime to turbulence were obtained. The result shows that f·Re is a function of Mach number and higher than incompressible value due to the compressibility effect. The values of f·Re were compared with f·Re correlations in available literature.

scholarly journals Two dimensional simulation of laminar flow by three- jet in a semi-confined space

2020 ◽  
Vol 9 (1) ◽  
pp. 111-117
Author(s):  
Mohammad Mosaddeghi
Keyword(s):  
Laminar Flow ◽  
Transient Flow ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Confined Space ◽  
Wide Range ◽  
Critical Reynolds Numbers ◽  
Dimensional Simulation ◽  
Geometric Changes

AbstractEquipment performance improvement in a wide range of working conditions is one of the major goals of aerodynamics. This goal can be achieved by the deformation of the object being examined or by using flow control techniques in active or inactive modes. In different researches, how to change the development ratio on the semi-confined space with input jet system is surveyed. In this study, two-dimensional simulation of the flow has been investigated in three-jet laminar flow in a semi-confined space. To determine the effective and optimal mixing in a laminar flow, critical Reynolds numbers were determined to distinguish when the flow in the channel from a steady-state symmetric flowformed downstream recirculation and ultimately transient flow. To better understand the flow characteristics, the simulations were changed at a fixed jet spacing (input jets distance to height of space ratio). Also, in this paper, for comparison, four jets were considered. Based on the results, it was observed that in all cases, mixing occurred in the space between three jets. Placing the jet along the walls of the semi-confined space allows the best combination, and increase in the distance between the first and third jets and reduction of the particle coefficient caused to reach the critical Reynolds number faster and, as a result, mixing in a laminar flow with geometric changes of the semi-confined space.

scholarly journals A simple two-dimensional parameterisation for Flux Footprint Prediction (FFP)

2015 ◽  
Vol 8 (11) ◽  
pp. 3695-3713 ◽  
Author(s):  
N. Kljun ◽  
P. Calanca ◽  
M. W. Rotach ◽  
H. P. Schmid
Keyword(s):  
Boundary Layer ◽  
Regional Scale ◽  
Particle Dispersion ◽  
Real Case ◽  
Observation System ◽  
Two Dimensional ◽  
Flux Footprint ◽  
Flux Tower ◽  
Wide Range ◽  
Flux Measurements

Abstract. Flux footprint models are often used for interpretation of flux tower measurements, to estimate position and size of surface source areas, and the relative contribution of passive scalar sources to measured fluxes. Accurate knowledge of footprints is of crucial importance for any upscaling exercises from single site flux measurements to local or regional scale. Hence, footprint models are ultimately also of considerable importance for improved greenhouse gas budgeting. With increasing numbers of flux towers within large monitoring networks such as FluxNet, ICOS (Integrated Carbon Observation System), NEON (National Ecological Observatory Network), or AmeriFlux, and with increasing temporal range of observations from such towers (of the order of decades) and availability of airborne flux measurements, there has been an increasing demand for reliable footprint estimation. Even though several sophisticated footprint models have been developed in recent years, most are still not suitable for application to long time series, due to their high computational demands. Existing fast footprint models, on the other hand, are based on surface layer theory and hence are of restricted validity for real-case applications. To remedy such shortcomings, we present the two-dimensional parameterisation for Flux Footprint Prediction (FFP), based on a novel scaling approach for the crosswind distribution of the flux footprint and on an improved version of the footprint parameterisation of Kljun et al. (2004b). Compared to the latter, FFP now provides not only the extent but also the width and shape of footprint estimates, and explicit consideration of the effects of the surface roughness length. The footprint parameterisation has been developed and evaluated using simulations of the backward Lagrangian stochastic particle dispersion model LPDM-B (Kljun et al., 2002). Like LPDM-B, the parameterisation is valid for a broad range of boundary layer conditions and measurement heights over the entire planetary boundary layer. Thus, it can provide footprint estimates for a wide range of real-case applications. The new footprint parameterisation requires input that can be easily determined from, for example, flux tower measurements or airborne flux data. FFP can be applied to data of long-term monitoring programmes as well as be used for quick footprint estimates in the field, or for designing new sites.

Prediction of Flow Separation in a Diffuser by a Boundary Layer Calculation

1977 ◽  
Vol 99 (2) ◽  
pp. 379-386 ◽  
Author(s):  
Y. Senoo ◽  
M. Nishi
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Shape Factor ◽  
Limit Relation ◽  
Performance Data ◽  
Separation Point ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Blockage Factor ◽  
Mean Pressure

From a consideration of flow stability, it is shown that the onset of separation in a diffuser depends upon the local blockage factor. Using performance data for two-dimensional diffusers from the literature, the shape factor of the boundary layer at the separation point Hs is related to the blockage factor Bs at that section, and the formula Hs = 1.8+3.75Bs is deduced as the separation-limit relation. It is proved that this separation-limit relation is also applicable to conical diffusers. Furthermore, a simple theory is derived to evaluate the time-mean pressure recovery in the separated region. Using this method, it is possible to predict whether a separation occurs in a diffuser and to evaluate the pressure recovery.

Modeling Oil Flows on Seal Runners and Engine Sump Walls

2004 ◽  
Vol 127 (4) ◽  
pp. 827-834 ◽  
Author(s):  
Masayoshi Shimo ◽  
James V. Canino ◽  
Stephen D. Heister
Keyword(s):  
Boundary Layer ◽  
Flow Behavior ◽  
Axial Direction ◽  
Outer Wall ◽  
Two Dimensional ◽  
Ambient Conditions ◽  
Boundary Layer Equations ◽  
Wide Range ◽  
Boundary Layer Method ◽  
Oil Flow

Oil flow behavior within a lubrication system utilized in a turbofan engine has been studied using a two-dimensional model for a seal runner and a sump wall. A two-dimensional, axisymmetric boundary layer method is utilized to derive a model for the film on the seal runner. An integral method analysis of boundary layer equations are utilized to derive a model for the film behavior on the outer wall of the sump neglecting variations in the axial direction. Parametric studies for oil flow at the seal runner and one the sump wall have been generated for a wide range of oil film properties and ambient conditions.

scholarly journals Multi-Fidelity Surrogate Models for Predicting Averaged Heat Transfer Coefficients on Endwall of Turbine Blades

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 482
Author(s):  
Woosung Choi ◽  
Kanmaniraja Radhakrishnan ◽  
Nam-Ho Kim ◽  
Jun Su Park
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Computing Time ◽  
Turbine Blades ◽  
High Fidelity ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
One Dimensional ◽  
Wide Range ◽  
Input Variables

This paper proposes a multi-fidelity surrogate (MFS) model for predicting the heat transfer coefficient (HTC) on the turbine blades. First, the low-fidelity (LF) and high-fidelity (HF) surrogates were built using LF-data from numerical simulation and HF-data from an experiment. To evaluate the prediction by these two surrogates, the averaged HTC distribution on the endwall of the gas turbine blade predicted by these two surrogates was compared for input variables as Reynolds number (Re) and boundary layer (BL) thickness. This shows that the prediction by LF surrogate is saturated with an increase in Re, while has monotonic behavior with an increase in BL thickness, which is contrary in general. The prediction by HF surrogate is linear with Re and is increased with BL thickness up to 30 mm and then decreased after 30 mm. Following this, a one-dimensional projection of the two-dimensional HTC distribution was presented to show the prediction tendency of the surrogates by varying the Re and fixing the BL thickness, and vice versa. Second, the MFS was built by combining the LF and HF data. The HTC distribution by the MFS model for the same input variables was shown with the HF data points. It is observed that the prediction by MFS is agreed well with the high-fidelity data. The MFS’s one-dimensional projection of the two-dimensional HTC distribution was compared with the LF surrogate prediction by varying the Re and fixing the BL thickness, and vice versa. This shows that the MFS model has more variations due to the included LF data. It is worth to mention that the averaged HTC distribution with an increase in boundary layer thickness predicted by the MFS is agreed well with the LF and HF data in the available dataset and has a large confidence interval between 30 and 50 mm due to the unavailable data in the specified range. To check the MFS accuracy, the root-mean-square error (RMSE) and error rate were evaluated to compare with the experimental uncertainty for a wide range of high-fidelity data. The present study shows that MFS would be expected to be an effective model for saving computing time and experimental costs.

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